Plug connector arrangement for optical fibers

ABSTRACT

In a plug arrangement for optical waveguides, there is mounted on the end of the cable accommodating the optical waveguide a cable fixing sleeve that is bonded to the outside of the cable. The ends of the plastic fibers of the optical waveguide cladding are brought out of the cable end and laid back onto the external surface of the bonded-on cable fixing sleeve and a further sleeve being pushed onto said cable fixing sleeve, with the plastic fibers of the optical waveguide cladding being clamped and bonded between the two sleeves.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/EP99/05526 which has an Internationalfiling date of Jul. 30, 1999, which designated the United States ofAmerica.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plug arrangement for opticalwaveguides in accordance with the preamble of the main claim.

2. Description of the Background Art

Plug arrangements of this type are known (U.S. Pat. No. 5,166,997). Theplastic fibers of the optical waveguide cladding that are brought out ofthe cable end and laid back on the external surface of the cable fixingsleeve are in this case clamped only between the cable fixing sleeve andthe further sleeve. Although it is already known, in a similar plugarrangement, to bond the cable fixing sleeve to the outside of the cable(JP-A-61-267007), the plastic fibers of the cladding are in this casealso only clamped between the cable fixing sleeve and the plug casing.This clamp fixing of the plastic fibers of the optical waveguidecladding does not ensure that the sensitive glass fibers, of the opticalwaveguides inside the plug casing, are held in a completely tension-freemanner without tensile or compressive loading of the cable end againstthe plug pins at the insertion end of the plug. There is the danger thatthe clamp fixing becomes detached or is not correctly fitted and thesensitive glass fibers are then damaged.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to disclose a plugarrangement for optical waveguides in which the sensitive opticalwaveguides are supported in a tensionfree manner in the plug casing, bya simple and inexpensively produced arrangement.

In accordance with the invention, prior to the fitting of the cable intothe cable housing, a sleeve unit comprising two mating sleeves is bondedonto the cable end, the ends of the aramid fibers enclosing the opticalwaveguides in the cable being concomitantly bonded between these twoindividual sleeves. Even before assembly, this provides a clean cableend in which the cladding fibers of the cable are uniformly bonded intothe sleeve unit and a uniform tension relief is already ensured thereby.As a result of the two interacting sleeve parts, the bonding can takeplace under pressure so that a firm joint of the sleeve parts to oneanother and to the aramid fibers and also to the cable end is achieved.It has proved particularly advantageous to provide a twist-proof toothstructure between the solder window sleeve held in a twist-proof manneron the contact carrier and the sleeve unit pushed onto the cable end andto design said tooth structure in such a way that it is not axialmovement that is necessary for its meshing but only lateral radialmovement.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 is a cross section of a plug arrangement according to anembodiment of the invention;

FIG. 2 is a cross section of a plug arrangement according to anotherembodiment of the invention;

FIG. 3 is a three-dimensional view of a sleeve; and

FIG. 4 is a three-dimensional view of a solder window sleeve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows, in section and on an enlarged scale, a first exemplaryembodiment of a plug arrangement according to the invention, comprisinga cylindrical metal plug casing 1 on which an axially displaceablecylindrical plug protector 2 is mounted. Provided at the insertion end 3of the plug is a contact carrier 4 in which the plug pins 5 for theoptical waveguides 6 and, optionally, also additional electrical contactpins 7 have been inserted. The contact carrier 4 is held in the casingby means of a solder window sleeve 8 that is inserted in the casing andis not completely closed, and on which a clamping nut 9, screwed in atthe cable connection end, acts in an axial direction. The clamping nut 9is screwed into the end of the plug casing 1 by means of an externalthread. Its internal edge 10 presses against the end of a collet 11whose clamping fingers, which are formed by slots, interact with anexternal tooth structure 12 of a metal cable fixing sleeve 13 by meansof an internal tooth structure. The thin-walled cylindrical portion 14of the cable fixing sleeve 13 is pushed over the end of the cable to beconnected with the interposition of cladding fibers 16 and the opticalwaveguide 6, of which only one is shown in the figure for the sake ofclarity. Formed inside the cable fixing sleeve 13 between thethin-walled portion 14 and a front, somewhat thickerwalled portion 23,is a stop shoulder 24. The outside of the thicker-walled portion 23 ofthe sleeve 13 is formed as a cone 17, the inside of the portion 23 beingcylindrical. Fitting onto the cone 17 is the internal cone of a furthermetal sleeve 18 that is cylindrical externally, and has an O-ring as aseal in a circumferential annular groove 19. Inserted between thecylindrical external surface of the sleeve 18 and the plug casing 1 is afurther sealing ring 20, that is made of metal, whose internalcylindrical surface rests against the sealing ring 19 and has anO-sealing ring in an external annular groove 21, located opposite of theinside of the plug casing. The end 22 of the collet 11 bears against thesealing ring 20, which is consequently clamped between the solder windowsleeve 8 and end portion 22 of the collet 11.

To assemble the plug arrangement, after the cable cladding end has beencut off, the optical waveguide or the optical waveguides 6 and thecladding fibers 16 are first laid bare. Then the thin-walled portion 14of the cable fixing sleeve 13 is pushed onto the cable end 15 with theinterposition of an adhesive, until the shoulder 24 comes up against thecut-off end face of the cable cladding. In this way, the sleeve 13 isfirmly bonded to the cable end. All the adhesives, standard inconnection with such optical waveguide arrangements, are suitable asadhesives for this purpose. The thickness of the portion 23 of thesleeve 13 is chosen so that the cylindrical internal diameter of thesleeve 13 is approximately equal to the diameter at which the claddingfibers 16 are distributed in the cable. The cladding fibers 16projecting from the sleeve are laid back over the edge of the sleeve 13onto the conical surface 17 and then the sleeves 18 are pushed into theposition shown and specifically, again with the interposition ofadhesive, so that the plastic fibers 16 are bonded to the two conicalsurfaces of the sleeves 13 and 18 under pressure. After bonding, thecladding fibers 16 projecting outwards from the bonding point betweenthe sleeves 13 and 18 can be cut off.

The ferrules for fixing the optical waveguides to the plug pins 5 arethen fitted on the optical waveguides 6 that project from the cable endprepared in this way, and the entire plug arrangement can then beassembled. The sealing ring 20 together with the collet 11 is insertedat the cable terminal end and the clamping nut 9 is then screwed intothe casing end. The tooth structure 12 is secured between collet 11 andcable fixing sleeve 13 by means of the collet 11 and the edge 10 of theclamping nut 9, which forces, by means of the collet 11, the cablefixing sleeve 13 together with the cable end into the plug casing 1until the end 22 of the collet 11 comes up against the sealing ring 20.The position of the cable end in the cable casing can be adjusted byaltering the axial position between collet 11 and cable fixing sleeve 13with the collet open. In the assembled state, the interior of the plugcasing is sealed by means of the sealing O-rings 19 and 21.

Instead of the additional sealing ring 20, the latter may also be formedin a directly integral manner with the sleeve 18. Under somecircumstances, such an additional sealing ring may also be dispensedwith entirely, the end portion 22 of the collet 11 then bears directlyagainst the edge of the solder window sleeve 8.

FIG. 2 shows a further exemplary embodiment of a plug arrangementaccording to the invention, identical parts being referenced with thesame reference symbols as in FIG. 1. The front end of the solder windowsleeve 8 is joined in a shape-locked manner, i.e. in a twist-proofmanner, to the contact carrier 4 by means of a metal ring 28 pushed ontothe contact carrier 4. The solder window sleeve 8 is, in accordance withFIG. 3, of only halfshell design and is not completely closed. Formed onits end face 26 is a tooth structure 27 that, in the example shown,comprises three narrow teeth that are arranged next to one another andwhose lateral teeth edges run parallel to one another. The teeththerefore have a constant width from the external circumference to theinternal circumference.

In the exemplary embodiment according to FIG. 2, the external surface 17of the cable fixing sleeve 13 is of cylindrical design and the furthersleeve 18 pushed onto the cable fixing sleeve 13 also has a cylindricalinternal surface at the bonding point. In addition, the sleeve 18 is ofintegral design and an additional sealing ring 20 as in FIG. 1 is notprovided. Provided on the outside of the sleeve 18 is an annular groovein which an O-ring 21 that interacts with the internal surface of theplug casing 1 is inserted as a seal. In accordance with FIG. 4, the endface of the sleeve 18 is provided with a crown-shaped circumferentialtooth structure 25 whose teeth, unlike the teeth 27 of the solder windowsleeve 8, have a trapezoidal cross section, i.e. the distance betweentwo adjacent teeth is greater at the external circumference than at theinternal circumference. The slit width between the teeth 25 is equal atthe internal circumference to the constant width of the central tooth ofthe tooth structure 27, the two adjacent teeth 27′ being designedsomewhat narrower than the central tooth. This configuration of theteeth 25 and 27 makes it possible that, with components 8 and 18arranged laterally next to one another, the teeth 27 can be pushed intothe tooth structure 25 in a radial direction (indicated by the arrow29), without the two parts 8 and 18 having to be displaced in the axialdirection. This avoids a tensile or compressive loading of the opticalwaveguide when the parts 8 and 18 are assembled. In the assembled state,the interaction of the tooth structures 25, 27 prevent a twisting of thesleeve unit 13, 18 with respect to the solder window sleeve 8 and,consequently, also with respect to the plug casing 1.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

What is claimed is:
 1. A plug arrangement for optical waveguides,wherein an end of a cable accommodating the optical waveguides is heldat a cable terminal end of a plug casing by a clamping nut, the opticalwaveguides that extend out at the cable end are routed to plug pins atan insertion end of the plug casing, wherein a cable fixing sleeve ismounted on the cable end and a further sleeve is mounted on the cablefixing sleeve, and the ends of plastic fibers of the cladding of theoptical waveguide that are brought out of the cable end are laid backonto an external surface of the cable fixing sleeve and are clampedbetween the cable fixing sleeve and the further sleeve, wherein thecable fixing sleeve is bonded on the outside of the cable and theplastic fibers of the optical waveguide cladding are also bonded betweenthe two sleeves, wherein an internal edge of the clamping nut pressesaxially against a bonded-on sleeve unit, such that an end face of thebonded-on sleeve unit, that is adjacent to an insertion end, interactswith an end face of a solder window sleeve disposed in the plug casing;wherein a solder window sleeve is joined in a twistproof manner to acontact carrier and two end faces of the sleeve unit, such that thesolder window sleeve interacts in a shape-locked manner; and wherein theend face of the sleeve unit has a crown-shaped tooth structure and theend face of the solder window sleeve that interacts therewith has apartial crown-shaped tooth structure; and wherein the interacting toothstructures are designed so that they can be enmeshed with one anotherwithout axial displacement in the radial direction.
 2. The plugarrangement according to claim 1, wherein a sealing ring is disposedbetween the outside of the bonded-on sleeve unit and the inside of theplug casing.
 3. The plug arrangement according to claim 1, wherein thecable fixing sleeve is designed at its end as a cone on the outside andthe internal surface of the mounted further sleeve has a matchingconical surface on the inside.
 4. The plug arrangement according toclaim 1, wherein a tooth structure that interacts with a tooth structureof a collet, held in the plug casing by the clamping nut, is formed onthe outside of the cable fixing sleeve.
 5. The plug arrangementaccording to claim 4, wherein an additional sealing ring bears axiallyon the plug casing and forms the bearing surface for the internal end ofthe collet, is disposed between the sleeve unit bonded-on at the cableend and the inside of the plug casing.
 6. The plug arrangement accordingto claim 1, wherein both the cable fixing sleeve and the further sleeve,mounted thereon and bonded thereto, are made of metal.
 7. A plugarrangement for optical waveguides, wherein an end of a cableaccommodating the optical waveguides is held at a cable terminal end ofa plug casing by a clamping nut, the optical waveguides that extend outat the cable end are routed to plug pins at an insertion end of the plugcasing, wherein a cable fixing sleeve is mounted on the cable end and afurther sleeve is mounted on the cable fixing sleeve, the ends ofplastic fibers of the cladding of the optical waveguide that are broughtout of the cable end are laid back onto an external surface of the cablefixing sleeve and are clamped between the cable fixing sleeve and thefurther sleeve, the cable fixing sleeve is bonded on the outside of thecable and the plastic fibers of the optical waveguide cladding are alsobonded between the two sleeves, and a tooth structure that interactswith a tooth structure of a collet held in the plug casing by theclamping nut is formed on the outside of the cable fixing sleeve.
 8. Aplug arrangement for fixedly holding optical waveguides of a opticalfiber, said plug arrangement comprising: a plug casing having a cableterminal end and an insertion end, said optical fiber being received atsaid insertion end of said plug casing; a cable fixing sleeve forreceiving an end of said optical fiber, said cable fixing sleeve beingbonded to an outermost surface of said optical fiber such that saidoptical waveguides are able to pass through an aperture of said cablefixing sleeve; a further sleeve having a receiving end and an end facehaving a crown-shaped tooth structure, said receiving end adapted toreceive a tapered portion of said cable fixing sleeve such that claddingof said optical fiber is fixedly held between said tapered portion ofsaid cable fixing sleeve and said receiving end of said further sleeve;a solder window sleeve joined in a twist-proof manner to a contactcarrier, said contact carrier adapted to receive said opticalwaveguides, said solder window sleeve having an end face that contains apartial crown-shaped tooth structure, wherein said end face of saidsolder window sleeve meshes with said end face of said further sleeve ina shape-locked manner without axial displacement in a radial direction;and a clamping nut adapted to be inserted in said plug casing at saidcable terminal end, such that said clamping nut is positioned betweensaid plug casing and said cable fixing sleeve, and operatively pressesaxially against said solder window sleeve, wherein said clamping nut,said solder window sleeve, said further sleeve and said cable fixingsleeve are all fixedly held in said plug casing.